This research project proposes to (1) isolate and characterize cell surface glycoproteins from normal and brachypod (bpH) cells undergoing chondrogenesis in vitro, and (2) investigate the biological relationship of the surface membrane components from these cells to the chondrogenic process. To accomplish these objectives the following will be carried out: (1) At three separate stages of culture (i.e., after attachment to the culture flask but before aggregation, after aggregation but before matrix deposition, and after matrix deposition) the surface glycoproteins will be released by trypsin treatment and characterized by molecular-sieve chromatography and SDS-polyacrylamide gel electrophoresis. (2) Surface membranes will be isolated by a combination of the Zn ions and polyethylene glycol-Dextran T-500 two phase separation techniques and their glycoproteins characterized by SDS-polyacrylamide gel electrophoresis for comparison with the glycoproteins obtained by trypsin treatment. (3) The incorporation of isotopic monosaccharides and amino acids into and their release from the surface glycoproteins of the genotypically different cells will be measured during culture. (4) Using morphological, histochemical, and biochemical parameters, the in vitro differentiation of limb mesenchyme in the presence of previously cultured cells of both genotypes will be examined. (5) Surface membranes and/or their glycoproteins will be added to cell cultures to establish whether any observed effects can be directly related to the cell surface. Information obtained from these experiments is expected to provide us with further insight into the role of cell surfaces during morphogenesis as well as enhance our understanding of cellular dysfunctions which produce birth defects.